Field of the Invention
The present invention relates to a sectorized beam operation in a wireless network, and in particular relates to a sectorized beam operation for reduced interference, enhanced robustness, and increased capacity in multiple, overlapping wireless networks deployment scenarios.
Description of the Related Art
FIG. 1 shows a CSMA-based wireless system with a basic service set 1 BSS-1, including an access point (AP) 10 and a station (STA) 20, and an overlapping basic service set 2 BSS-2, including an access point AP 11 and a station STA 21. The coverage 30 of the basic service set BBS-1 overlaps a part of the coverage 31 of the basic service set BBS-2. The two BSSs are called, overlapping BSS, OBSS. When any of the access points APs 10, 11 or station STAs 20, 21 tries to access the channels for wireless transmission, it performs a channel sensing and a random back-off contention procedure. Any of the station or access point wins the contention can transmit into the wireless medium to gain the transmit opportunities (TXOP) and other stations or access point sense that the channel is busy would defer their transmission until the TXOP is over. Such carrier sense multiple access, (CSMA,) wireless protocol minimizes the likelihood of collision in which more than one station or access point transmit into the wireless medium causing the reception at the intended recipient to fail. In general, the CSMA protocol is intended for devices (station or access point) with omni-direction antennas such that the all the devices sharing the wireless medium can hear one another. However, if one device cannot hear another device in the same wireless medium, it is called a hidden node. With a hidden node in the wireless network, potential collision can occur since the device is unable to sense the transmission of the other devices. Note that since the two wireless networks (e.g. BSS-1 and BSS-2 in this example) are sharing the same wireless medium for transmission, the achievable throughput of each individual network is reduced whereas the aggregate network throughput of the two wireless networks remains approximately the same. For long range outdoor networks, the increased coverage range results in many overlapping wireless networks within the same area leading to significant reduction in the throughput of the individual network. Therefore, there's a need to manage the communication in wireless networks with overlapping coverage.